Gastritis as an immunotherapy-related toxicity in the treatment of endometrial cancer: A case report.

Gastritis related to immunotherapy use is a less commonly reported adverse effect. With increasing use of immunotherapy agents in the management of patients with endometrial cancer, even rare adverse effects are being seen more frequently in gynecologic oncology practice. A 66-year-old with recurrent mismatch repair deficient endometrial cancer was treated with single-agent pembrolizumab. She initially appeared to tolerate treatment well; however after 16 months of therapy she began to develop nausea, vomiting, and abdominal pain that resulted in 30-pound weight loss. Pembrolizumab was held out of concern for immunotherapy related toxicity. She underwent evaluation with gastroenterology including esophagogastroduodenoscopy (EGD) with biopsy that demonstrated severe lymphocytic gastritis. She was treated with IV methylprednisolone with improvement in symptoms over three days. She was then transitioned to oral prednisone at 60 mg daily with weekly taper by 10 mg, with a proton pump inhibitor (PPI) and carafate until resolution of symptoms. She subsequently had a follow up EGD with biopsy, which demonstrated resolving gastritis. She is presently doing well off of steroids with stable disease noted on her last scan after cessation of pembrolizumab.